Assembly for implanting an acetabular cup in a cotyloid cavity

ABSTRACT

The present invention relates to an assembly having a acetabular cup has at least two snapping rims; the gripper is a subassembly separated from the handle, including a snapping teeth suitable for engaging with the snapping rims included by the acetabular cup. The gripper includes a movable pusher, capable, during its movement, of exerting thrust on the acetabular cup along the axis of revolution of said acetabular cup, so as to disengage the snapping rims comprised by the acetabular cup from their engagement with the snapping teeth included by the gripper; and the assembly includes an actuating device for actuating the movable pusher.

TECHNICAL FIELD

The present invention relates to an assembly for implanting anacetabular cup in a cotyloid cavity. The term “acetabular cup” used inthe present description designates the outer part of a cotyloid implant,generally made from metal, intended to be impacted in said cotyloidcavity in a patient's pelvis. This cotyloid implant comprises, asidefrom this outer shell, and according to a well-known technique that doesnot need to be described, an inner sliding core, in particular made fromhigh-density polyethylene, forming an articulation cavity for a femoralhead supported by a femoral rod implanted in the femur.

BACKGROUND OF THE INVENTION

As one knows, a patient's pelvis bone may wear out over time at itsparts defining the cotyloid cavity, thus requiring the placement of acotyloid implant reforming the cotyloid cavity in order to receive theprosthetic femoral articulation head.

In order to be placed perfectly in the cotyloid cavity, the cotyloidimplant must be impacted in a cavity, which is done using an instrumentcomprising a gripping head for the acetabular cup and ahandling/impacting handle for that acetabular cup.

For example, patent application publication no. WO 2004/069107 describesan acetabular cup with a proximal inner groove and an instrumentcomprising a gripping head secured to a handle. The gripping head isequipped with radially movable locking tabs, which engage in the grooveof the acetabular cup in order to assemble the acetabular cup thereon,and which are capable to be withdrawn using a handle, to release theacetabular cup.

Such an instrument has a complex structure, and is therefore expensiveto manufacture. Furthermore, this instrument must be carefullysterilized between two surgical procedures, in particular at the manyinterstitial spaces comprised by the gripping head, which affects theusage cost of this instrument.

The present invention aims to resolve this drawback.

Patent application publications nos. US 2007/219562, WO 86/05384 andU.S. Pat. No. 6,468,281 describe similar instruments, with grippingheads secured to handles, these instruments further comprising distalbearing heads coming into contact with the bottom of the acetabular cupsto distribute the impact force. The same comments as above can be maderegarding the assemblies described by these documents.

OBJECT OF THE INVENTION

The present invention precisely aims to resolve the aforementioneddrawbacks of the existing assemblies.

SUMMARY OF THE INVENTION

According to the invention, the assembly comprises:

an acetabular cup, intended to be implanted in a cotyloid cavity of apatient's pelvis, and

a gripping/impacting instrument for the acetabular cup, comprising:

a gripper, having an appropriate surface to come into contact with theacetabular cup, and equipped with reversible retaining members forreversibly retaining the acetabular cup, and

a gripping/impacting handle;

the acetabular cup has at least two snapping rims;

the gripper is a subassembly separated from the handle and capable to beassembled to said handle, comprising means for connecting to the handle;

the handle is a separate subassembly from the gripper and capable to beassembled to the gripper, comprising connecting means for connecting tothe gripper, capable to cooperate with the connecting means comprised bythe gripper to connect said handle to said gripper;

the reversible retaining members are in the form of snapping teethsuitable for engaging with the snapping rims comprised by the acetabularcup and releasing the acetabular cup following a thrust exerted on theacetabular cup substantially along the axis of revolution of thatacetabular cup;

the gripper comprises a movable pusher, movable from a withdrawnposition not hindering the assembly of the acetabular cup to thegripper, toward an extension position, this pusher exerting, during thismovement, thrust on the acetabular cup substantially along the axis ofrevolution of said acetabular cup, so as to disengage the snapping rimscomprised by the acetabular cup from their engagement with the snappingteeth comprised by the gripper; and

the assembly comprises means for actuating the movable pusher, making itpossible to move that pusher from said withdrawn position to saidextension position.

The gripper is thus formed by a subassembly separable from the handle,such that it is capable to be assembled to the acetabular cup by themanufacturer of the acetabular cup, then to be sterilized and packagedwith that acetabular cup. During use, the practitioner opens thispackage and brings the respective connecting means of the handle and thegripper into a mutual assembly state, which allows him/her to form thegripping/impacting instrument for the acetabular cup; once the impactingis done, this practitioner acts on the actuating means of the pusher soas to move said pusher toward said extension position, and in so doing,to separate the acetabular cup from the gripper.

This instrument structure thus makes it possible to give the gripper asimplified structure, in particular making it possible for this gripperto be intended for a single use. As a result, the sterilizationrequirements for the instrument only relate to the handle, and aregreatly reduced.

Furthermore, the assembly according to the invention allows theacetabular cup to be ejected from the gripper, therefore allowing aseparation of the instrument and the acetabular cup that does not riskaffecting the position of the acetabular cup in the equipped cavity.

The gripper may in particular be formed by a single part made by moldingor machining a synthetic material, said snapping teeth being integralwith the rest of the gripper.

This gripper is thus particularly inexpensive to produce.

It would be conceivable for said actuating means of the movable pusherto be of the piston or screwing/unscrewing type, for example actingthrough the handle, which would be tubular.

Furthermore, it would be conceivable for said connecting meansconnecting the handle to the gripper to be in the form of a screwedconnection; for example, a tubular sleeve as cited above would beoutwardly threaded and capable to be assembled to the gripper byscrewing.

However, according to one preferred embodiment of the invention:

the connecting means for connecting the gripper to the handle comprise:

an assembly cavity arranged in the gripper and an assembly head securedto the handle, this assembly head forming an extension capable to bereceived in an adjusted manner in the assembly cavity;

first locking recesses arranged in the walls defining said assemblycavity and second locking recesses arranged in the side walls of saidextension, the first and second recesses coming opposite one another inthe assembly position of the gripper to the handle;

a movable locking/thrust part, capable to be moved in said extension,that forms third recesses capable to come opposite said second recesses,and that has flats situated near these third recesses, on the proximalside relative thereto;

an elastically deformable shank or other similar expansive element,engaged and retained in said first recesses or in said second recesses,this shank being deformable between a contracted state, in which it doesnot hinder the engagement and sliding of said extension in said assemblycavity, and a not deformed state, in which it extends both in said firstrecesses and in said second recesses, thus performing a reversibleretention of said extension in said assembly cavity and therefore areversible assembly of the gripper to the handle;

said locking/thrust part being movable between a position not lockingthe assembly of the gripper to the handle, in which said third recessesare opposite the shank and allow the deformation of said shank in saidcontracted state, therefore allowing said reversible assembly of thegripper to the handle, and a position locking the assembly of thegripper to the handle, in which said flats comprised by thislocking/thrust part are opposite the shank and prohibit the deformationof said shank in said contracted state, therefore locking the assemblyof the gripper to the handle;

said movable pusher is situated opposite said assembly cavity; and

the actuating means of the pusher include said locking/thrust part,which is movable between said locking position and a bearing position inwhich it bears against the movable pusher so as to move said pushertoward said extension position.

Thus, the assembly of the handle to the gripper is done simply, byengaging said extension comprised by the assembly head in said assemblycavity, until the shank is engaged in said first and second recesses, byelastic return of said shank. The handle is then reversibly connected tothe gripper, sufficiently to grasp the gripper-acetabular cup assemblyand bring this assembly toward the cotyloid cavity to be equipped.

Once the impacting of the acetabular cup is done in the cotyloid cavity,the practitioner acts on the actuating means so as to move saidlocking/thrust part toward said locking position of the connection ofthe gripper to the handle, then toward said bearing position, so as toeject the acetabular cup. Consequently, the connection of the gripper tothe handle is locked before the force necessary to eject the acetabularcup begins to be exerted on the connection of the acetabular cup to thegripper.

The invention thus provides connecting means that are easy to use,acting through simple inter-engagement, and the maintained engagement ofwhich is provided automatically when the acetabular cup is ejected.There is therefore no risk of these connecting means releasingthemselves rather than the snapping connection of the acetabular cup tothe gripper being released.

It must be emphasized that for clarity of the present description, ithas been stated that said assembly cavity is arranged on the gripper andsaid extension is arranged on the assembly head; it would in fact beconceivable for said cavity to be arranged in the assembly head and forthe gripper to form said extension.

Preferably, said actuating means include, aside from said locking/thrustpart, a lever mounted pivoting on the handle and a connecting rodconnecting this lever to the locking/thrust part, said connecting rodperforming, during the pivoting of the lever, the movement of saidlocking/thrust part between said non-locking and bearing positions.

According to one simple embodiment of the invention,

the gripper comprises a bore in which the movable pusher is engaged andis capable to slide;

the movable pusher is formed by a cylindrical part having two circularribs protruding from its wall, these ribs being situated at a distancefrom one another at least equal to the travel of the pusher between itsaforementioned withdrawn and extended positions;

the gripper is made from a slightly elastically deformable material,such as a synthetic material, allowing the engagement of one of saidcircular ribs through said bore and the retention of the movable pusheron the gripper by elastic return of the material making up the gripperaround the wall portion of the movable pusher situated between the tworibs.

The gripper and the movable pusher thus have simple structures, and theassembly of the movable pusher on the gripper is done simply.

Advantageously, the extension forms, at its end intended to be turnedtoward the movable pusher, a surrounding end-piece capable to engage onthe movable pusher.

This engagement of the extension with the movable pusher ensures perfectguidance of this pusher when the locking/thrust part bears against thispusher during its movement.

The invention will be well understood, and other features and advantagesthereof will appear, in reference to the appended diagrammatic drawing,described below; this drawing shows, as a non-limiting example, onepreferred embodiment of the assembly in question.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of this assembly, in a first position of a leverthat it comprises;

FIG. 2 is a view similar to FIG. 1, in a second position of the lever;

FIG. 3 is an enlarged perspective view of an assembly head that itcomprises;

FIG. 4 is an enlarged side view of a gripper and acetabular cup that itcomprises;

FIG. 5 is a sectional view of the gripper along line V-V of FIG. 4;

FIG. 6 is a view of the gripper similar to FIG. 5, after engagement ofan extension comprised by the assembly head in a cavity comprised by thegripper;

FIG. 7 is a sectional side view, passing through the axis of theacetabular cup, of an assembly head comprised by the handle, the gripperand the acetabular cup, in a non-assembly position of the head and thegripper, with a detail circled;

FIG. 7A is a view of the circled detail of FIG. 7;

FIGS. 8 and 8A are views similar to FIGS. 7 and 7A, respectively, in anunlocked assembly position of said assembly head to the gripper;

FIGS. 9 and 9A are views similar to FIGS. 8 and 8A, respectively, in alocked assembly position of said assembly head to the gripper and in aposition of ejection of the acetabular cup; and

FIGS. 10 and 10A are views similar to FIGS. 9 and 9A, respectively, in areturn position of said assembly head and said gripper to an unlockedassembly position, while the acetabular cup has been ejected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show an assembly 1 for implanting a prosthetic acetabularcup 2 in a cotyloid cavity, this cavity being defined by the pelvis bone100 of a patient, as shown diagrammatically in FIGS. 9 and 10.

In addition to the acetabular cup 2, the assembly 1 comprises a gripper3 and a handle 4.

The acetabular cup 2 is formed, in a manner well known in itself, by ametal shell having, in the illustrated example, a substantiallyhemispherical shape and a smooth and continuous wall. The cavityinwardly defined by this acetabular cup 2 is intended to receive asliding core (not shown), in particular made from high-densitypolyethylene, forming an articulation cavity for a femoral headsupported by a femoral rod implanted in the femur.

The acetabular cup 2 has, at its equatorial edge and at its outer face,five recesses 5 regularly distributed over its circumference, formingrounded snapping ribs, visible in FIGS. 9 and 10.

The gripper 3, more particularly visible in FIGS. 4 and following, isformed by a single piece of molded or machined synthetic material. Itcomprises a flat proximal part 3a and a distal axial boss 3 b, and formsan assembly cavity 6. At the walls defining the cavity 6, firstelongated recesses 7 are arranged.

The flat proximal part 3 a forms a peripheral surface intended to bearagainst the equatorial rim of the acetabular cavity 2, and the distalaxial boss 2 b forms an axial bore, in which a pusher 10 is slidinglyengaged.

It appears that this pusher 10 is formed by a cylindrical part havingtwo circular ribs protruding from its wall, these ribs being situated ata distance from one another. As appears by comparing FIGS. 7 and 9, thisdistance is slightly larger than a travel of the pusher 10 between awithdrawn position shown in FIG. 5 and an extension position shown inFIG. 7.

It will also be understood that the material making up the pusher 10and/or the gripper 3 is slightly elastically deformable, so as to allowthe forced engagement of the distal circular ribs through said bore, theretention of the pusher 10 on the gripper 3 resulting from the elasticreturn of the material making up the gripper 3 around the wall portionof the pusher 10 situated between the two ribs. To facilitate theengagement of said rib, the gripper 3 forms an inlet basin at the wallsdefining the bottom of the cavity 6.

The gripper 3 also comprises, at the peripheral edge of its proximalpart 3a, snapping teeth 11 intended to match recesses 5, these teeth 11forming rounded inner ribs intended to engage by snapping with the ribsformed by the wall of the acetabular cup 2 at the recesses 5, as inparticular shown in FIGS. 4 and 7.

It appears that, in said withdrawn position of the pusher 10, shown inFIG. 7, the pusher 10 does not hinder the snapping of the teeth 11 onthe ribs formed by the acetabular cup 2, and the distal end of thepusher is withdrawn from the bottom of the acetabular cup 2.

It also appears that the rounded shape of the respective rims of theteeth 11 and the acetabular cup 2 allows the snapping engagement to bereversible in that it is released when the pusher 10 is moved toward itsextension position and therefore bears against the bottom of theacetabular cup 2, as will be understood by comparing FIGS. 7 and 9.

In reference again to FIGS. 1 and 2, it appears that the handle 4comprises a proximal anvil 15, a gripping handle 16 and an assembly head17 for assembly to the gripper 3.

The anvil 15 is intended to be struck using a mallet during theimpacting of the acetabular cup 2 in the cotyloid cavity, while thehandle 4 is maintained using the grip 16.

As shown, the handle 4 is equipped, at this grip 16, with a lever 20mounted pivoting around a pin 21, which lever 20 is pivotably connected,using a pin 22 separate from the pin 21 and having an axis differentfrom the latter, to a connecting rod 23. On the side of the head 17, theconnecting rod 23 is connected to a locking/thrust part 25, movableinside the head 17, using a pin 24.

Due to the shift of the two pins 21 and 22, it will be understood thatthe pivoting of the lever 20 from the position shown in FIG. 1 towardthe position shown in FIG. 2 causes a translation of the connecting rod23 in the distal direction, which is transmitted to the locking/thrustpart 25 and moves that part through the head 17, as described later.

In reference to FIGS. 3, 7 and 8, it appears that the head 17 has anaxial extension 26 being integral therewith, capable to be engaged inthe cavity 6 in an adjusted manner. This axial extension 26 has recesses27, in which an elastically deformable metal shank 30 is placed.

As shown in FIG. 3, this shank is U-shaped, having an intermediaterectilinear branch and two curved side branches, and is engaged in therecesses 27. It appears in FIG. 6 that the side branches of the shank 30are configured so as to be capable to engage in the recesses 7 formed bythe gripper 3 at its walls defining said cavity. This shank 30 isdeformable between a normal, non-deformed state, visible in FIGS. 3 and6, and a contracted state, in which its side branches are closer to oneanother, inside the recesses 27, the latter having a depth of allowingthis closer position of said side branches, as shown in FIGS. 7A and 8A.

It further appears that the extension 26 forms, on its distal side, asurrounding end-piece capable to engage on the proximal end of thepusher 10.

As shown in FIGS. 3, 6 and 7A, the locking/thrust part 25 has two siderims situated on two opposite sides, which are beveled at their distalends so as to form recesses 31 and which have, on the proximal siderelative to these recesses 31 and immediately above them, outer facesforming flats 32.

As shown in FIGS. 7 and 7A, before the handle 4 is assembled to thegripper 3, the shank 30 is in its non-deformed state, in which itpartially protrudes beyond the wall of the extension 26 (see FIG. 7A);when the extension 26 is engaged in the cavity 6, the side branches ofthe shank 30 encounter the walls of the gripper 3 defining the cavity 6and are therefore brought closer to one another while being moved in thebottom of the recesses 27. When the head 17 is in the position assembledto the gripper 3, as shown in FIGS. 8 and 8A, the recesses 27 comeopposite the recesses 7 and the shank 30 then tends to regain itsoriginal shape by elastic return, such that its side branches engageboth in the recesses 27 and in the recesses 7 (see FIG. 8A).

The handle 4 is then connected to the gripper 3, this connection beingsufficient to grasp the gripper 3-acetabular cup 2 assembly and bringthis assembly toward the cotyloid cavity to be equipped. This connectionis, however, reversible because of the rounded shapes that the recesses7 and the shank 30 have in cross-section, such that the separation ofthe gripper 3-acetabular cup 2 assembly with respect to the handle 4remains possible if necessary.

Once the acetabular cup 2 is impacted in the cotyloid cavity, thepractitioner acts on the lever 2 so as to move the locking/thrust part25 in the distal direction, which, over a first part of the travel ofthis part 25, brings the flats 32 across from the side branches of theshank 30 and keeps these side branches engaged in the recesses 7, asshown in FIG. 9A; the connection between the handle 4 and the gripper 3is thus locked. Over the second part of the travel of the part 25 in thedistal direction, and while the flats 32 are still across from the sidebranches of the shank 30, the part 25 bears against the proximal end ofthe pusher 10 and moves the latter. During this movement, the distal endof the pusher 10 encounters the bottom of the acetabular cup 2 and bearsagainst this bottom so as to release the acetabular cup 2 with respectto the teeth 11.

Consequently, the connection of the gripper 3 to the handle 4 is lockedbefore the force necessary to eject the acetabular cup 2 begins to beexerted on the connection of the acetabular cup 2 to the gripper 3.

As appears from the preceding, the invention provides an assembly forimplanting an acetabular cup in a cotyloid cavity having decisiveadvantages with respect to its counterpart assemblies of the prior art.Indeed, because the gripper 3 is formed by a subassembly that can beseparated from the handle 4, it has a simpler structure, making itpossible for this gripper to be intended for a single use, which greatlyreduces the sterilization requirements, which then only pertain to thehandle. Furthermore, the assembly according to the invention allows theacetabular cup to be ejected with respect to the gripper, thereforeallowing a separation of the instrument and the acetabular cup that doesnot risk affecting the position of the acetabular cup in the equippedcavity.

What is claimed is:
 1. An assembly for implanting an acetabular cup in acotyloid cavity, the assembly comprising: the acetabular cup, intendedto be implanted in a cotyloid cavity of a patient's pelvis, and agripping and impacting instrument for the acetabular cup, the instrumentcomprising: a gripper having a surface to come into contact with theacetabular cup, the gripper includes reversible retaining members forreversibly retaining the acetabular cup, and a gripping/impactinghandle; the acetabular cup has at least two snapping rims; the gripperis separated from the handle and capable to be assembled to said handle,the gripper comprising a connecting device to the handle; the handle isa separate subassembly from the gripper and capable to be assembled tothe gripper, the handle comprising connecting piece for connecting tothe gripper, capable to cooperate with the connecting device of thegripper to connect said handle to said gripper; the reversible retainingmembers are in the form of snapping teeth suitable for engaging with thesnapping rims comprised by the acetabular cup and releasing theacetabular cup following a thrust exerted on the acetabular cup alongthe axis of revolution of that acetabular cup; the gripper comprises amovable pusher, movable from a withdrawn position not hindering theassembly of the acetabular cup to the gripper, toward an extensionposition, the pusher exerting, during the movement, thrust on theacetabular cup along the axis of revolution of said acetabular cup, soas to disengage the snapping rims comprised by the acetabular cup fromthe engagement with the snapping teeth comprised by the gripper; and theassembly comprises actuating devices for actuating the movable pusher,making it possible to move that pusher from said withdrawn position tosaid extension position.
 2. The assembly according to claim 1, whereinthe gripper is form by a single part made by molding or machining asynthetic material, said snapping teeth being integral with the rest ofthe gripper.
 3. The assembly according to claim 1, wherein: theconnecting device for connecting the gripper to the handle comprise: anassembly cavity arranged in the gripper and an assembly head secured tothe handle, this assembly head forming an extension capable to bereceived in an adjusted manner in the assembly cavity; first lockingrecesses arranged in the walls defining said assembly cavity and secondlocking recesses arranged in the side walls of said extension, the firstand second recesses coming opposite one another in the assembly positionof the gripper to the handle; a movable locking/thrust part, capable tobe moved in said extension, that forms third recesses capable to comeopposite said second recesses, and that has flats situated near thesethird recesses, on the proximal side relative thereto; an elasticallydeformable shank or other similar expansive element, engaged andretained in said first recesses or in said second recesses, the shankbeing deformable between a contracted state, in which it does not hinderthe engagement and sliding of said extension in said assembly cavity,and a not deformed state, in which it extends both in said firstrecesses and in said second recesses, thus performing a reversibleretention of said extension in said assembly cavity and therefore areversible assembly of the gripper to the handle; wherein saidlocking/thrust part being movable between a position not locking theassembly of the gripper to the handle, in which said third recesses areopposite the shank and allow the deformation of said shank in saidcontracted state, therefore allowing said reversible assembly of thegripper to the handle, and a position locking the assembly of thegripper to the handle, in which said flats comprised by thislocking/thrust part are opposite the shank and prohibit the deformationof said shank in said contracted state, therefore locking the assemblyof the gripper to the handle; said movable pusher is situated oppositesaid assembly cavity; and the actuating device of the pusher includesaid locking/thrust part, which is movable between said locking positionand a bearing position in which it bears against the movable pusher soas to move said pusher toward said extension position.
 4. The assemblyaccording to claim 1, wherein said actuating device includes, aside fromsaid locking/thrust part, a lever mounted pivoting on the handle and aconnecting rod connecting this lever to the locking/thrust part, saidconnecting rod performing, during the pivoting of the lever, themovement of said locking/thrust part between said non-locking andbearing positions.
 5. The assembly according to claim 1, wherein thegripper comprises a bore in which the movable pusher is engaged and iscapable to slide; the movable pusher is formed by a cylindrical parthaving two circular ribs protruding from its wall, these ribs beingsituated at a distance from one another at least equal to the travel ofthe pusher between its aforementioned withdrawn and extended positions;the gripper is made from a slightly elastically deformable material,such as a synthetic material, allowing the engagement of one of saidcircular ribs through said bore and the retention of the movable pusheron the gripper by elastic return of the material making up the gripperaround the wall portion of the movable pusher situated between the tworibs.
 6. The assembly according to claim 1, wherein the extension forms,at its end intended to be turned toward the movable pusher, asurrounding end-piece capable to engage on the movable pusher.